The field of the disclosure relates generally to devices and methods for containing potentially releasable components from rotatable machines and, more particularly, a containment case for a gas turbine engine fan assembly configured to dissipate impact energy from a released fan blade.
At least some known rotatable machines such as gas turbine engines include rotating components mounted to shafts and surrounded by shrouds and casings that provide structural support and air flow guidance through the machine. The rotating components, including the blades of fans, compressors, and turbines, for example, rotate with a tip of the respective component passing very close to the shrouds or casings. During some events, for example, a bird ingestion into the gas turbine engine, the blades may contact the shrouds or casings. Also, during at least some such events, the blades may be released from gas turbine engines, i.e., “fan blade out” (FBO), and pose a threat to operators and bystanders as projectiles. Such events also typically cause damage to the shrouds or casings of the blades and to other components of gas turbine engines. The damage may also cause the gas turbine engine to operate with a lesser capability, necessitating repair.
To facilitate mitigating such damage and possibly forestalling immediate repair necessity, some shrouds or casings are equipped with abradable material that circumscribe at least some of the rotating components, such as, the fan blades. The abradable material serves to form a portion of the flow path of the fan assembly. However, during an event where the blade is released and contacts the abradable material of the fan casing, the abradable material at least partially yields, dissipating projectile energy of the released blade and minimizing damage to the gas turbine engine. The abradable material is designed to be relatively easy to replace or repair such that total maintenance time to repair the casing after an event, e.g., an FBO, is minimized. However, at least some known abradable materials are constructed of paper and, thus, are not easily tailored in terms of physical characteristics including sheer stiffness. Such known abradable materials require increased weight and space to achieve increased sheer stiffness for effective energy dissipation upon impact of released components in rotatable machines such as gas turbine engines.